1. Field of the Invention
The present invention relates to an electrical proximity switch arrangement and is more particularly concerned with the installation and protection of proximity switches or the like, i.e. solid state devices which are actuated by approaching or touching with the hand conductive plate so as to generate a signal which, properly amplified, will in turn provide a control signal, such as for activating or de-activating associated equipment.
2. Description of the Prior Art
Proximity switches heretofore known in the art have exhibited a number of disadvantages, both as regards installation and safety. Some of the known switches operate on the basis of the conduction of an electric current when the conductive plate is touched. As a result, there will be an electrical connection, even though through a large resistance, between the plate and the internal circuit. The said connection is attained by piercing the wall of an insulating support plate, to which the conductive plate is secured, and making a connecting conductor pass through the hole formed by the piercing operation, the conductor extending from this plate to a portion of the circuit. Such portion of the circuit is necessarily mounted on the rear face of the insulating support plate. The remaining portion of the circuit is enclosed within a separate housing which is connected to the first-mentioned portion by means of pins or coupling connectors.
The above-described prior art arrangement is complicated and expensive, and moreover presents an obstacle to modular production of the different units, along with difficulty in installation and large overall dimensions.
In addition, the said electrical connection from the conductive plate, even though through a large resistance, always results in danger to the user. The circuits are fed by the mains or network voltage so that there is always a risk that, for some incidental cause, the connecting conductor will transmit the whole voltage to the conductive plate, with serious consequences for the user.